O7.5 Sleep related breathing disorders

COPD has adverse effects on sleep quality, resulting in poor sleep efficiency, delayed sleep onset, multiple waken­ings with fragmentation of sleep architecture, and a high arousal index. Arousals are caused by hypoxia, hypercap­nia, nocturnal cough and the pharmacological effects of methylxanthines and b-adrenergic agents (Phillipson 1986). Intranasal oxy­gen administration has been shown to improve sleep archi­tecture and efficiency, as well as oxygen saturation during sleep (Meecham Jones 1995).

Indications for full diagnostic polysomnography in patients with COPD include persistent snoring, witnessed apnoeas, choking episodes and excessive daytime sleepiness. In subjects with daytime hypercapnia, monitoring of noctur­nal transcutaneous carbon dioxide levels should be consid­ered to assess nocturnal hypoventilation. Patients with COPD with a stable wakeful PaO2 of more than 55mmHg (7.3kPa) who have pulmonary hypertension, right heart failure or polycythaemia should also be studied. Overnight pulse oximetry is also useful in patients with COPD in whom long-term domiciliary oxygen therapy is indicated (stable PaO2 <55mmHg, or 7.3kPa) to determine an appropriate oxygen flow rate during sleep.

The overlap syndrome: The combination of COPD and obstructive sleep apnoea (OSA) is known as the “overlap syndrome” (McNicholas 2009) [evidence level III-2]. The prevalence of COPD in unselected patients with OSA is about 10%, while about 20% of patients with COPD also have OSA (Chaouat 1995). Patients with COPD who also have OSA have a higher prevalence of pulmonary hypertension and right ventricular failure than those without OSA (Chaouat 1995).  Results of a longitudinal observational study suggest that COPD patients with overlapping OSA have higher mortality and more frequent exacerbations of their disease than COPD patients without OSA [evidence level III-2].  CPAP treatment reduced mortality and exacerbation rates (Marin 2010) [evidence level III-2].  While oxygen administration may diminish the degree of oxygen desaturation, it may increase the frequency and severity of hypoventilation and lead to carbon dioxide retention.

As in other patients with OSA, weight reduction, alcohol avoidance and improvement of nasal patency are useful in those with COPD. Nasal continuous positive airway pres­sure (CPAP) is the best method for maintaining patency of the upper airway and may obviate the need for nocturnal oxygen. If nasal CPAP is not effective, then nocturnal bi-level positive airway pressure ventilation should be considered, although the benefits of this in chronic stable COPD remain to be established. The role of other OSA treatments, such as mandibular advancement splinting, remains to be evaluated in the overlap syndrome.